This invention relates to polyketone polymer compositions. More particularly, this invention relates to polyketone polymer compositions containing a stabilizer acting against heat degradation during their end-use.
Polymers of carbon monoxide and olefinically unsaturated compounds generally referred to as polyketones or polyketone polymers are well known in the art. The class of linear alternating polymers of carbon monoxide and at least one unsaturated compound are of particular interest among polyketone polymers. In the linear alternating polymers the units originating from carbon monoxide alternate with the units originating from the olefinically unsaturated compound(s). This class of polymers is disclosed in numerous patent documents, exemplified by U.S. Pat. No. 4,880,865 and U.S. Pat. No. 4,818,811.
EP-A-289077 discloses compositions of the poly-ketone polymers containing active phenolic stabilizers selected from a few small groups of narrowly defined additives. Phenolic stabilizers exemplified in the working examples of EP-A-289077 are triethyleneglycol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate] and 1,6-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propaneamido]hexane. These stabilizers have in common a moiety of a phenolic carboxylic acid and they differ from each other in that one is a di-ester of triethylene glycol while the other is a di-amide derived from hexamethylenediamine. They give the polyketone polymer compositions an attractive level of stability against heat degradation during their end-use as judged from the retention of the mechanical properties. In the comparative examples of EP-A-289077 octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate and pentraerythrityl tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate] failed to show an attractive performance in the polyketone polymers. These additives are alkanol mono- and tetra-esters derived from a moiety of the same phenolic carboxylic acid.
Thus, it has correctly been said in EP-A-289077 that the invention in question relates to a selection of stabilizers from "a few small groups of narrowly defined additives".
The stabilised compositions described in EP-A-289077 have some practical problems associated with them. For example, compositions which contain triethyleneglycol bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate] are difficult in melt processing operations which extend over a longer period of time, for example a time in excess of one hour. In injection moulding trials the transport of polymer melt ceases due to slipping of the screw. Further, compositions which contain 1,6-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propaneamido]hexane and objects made of the compositions develop a yellow discoloration relatively rapidly when they are exposed to heat, such as during melt processing and during their end-use. Thus, there is a need for finding adequate stabilizers for the polyketone polymers which do not have the aforementioned disadvantages.
It is an unexpected finding that, despite the teaching of EP-A-289077, certain phenolic alkylene dicarboxylates, which are alkanol di-esters of the same type of phenolic carboxylic acid as mentioned above, not only provide an attractive level of stabilization of the polyketone polymer compositions against heat degradation with a much reduced tendency to yellow discoloration, they also provide polyketone polymer compositions with an attractive melt processing performance over an extended period of time, and with an attractive level of physical and mechanical properties.
The finding is indeed surprising as it was found that another phenolic alkylene dicarboxylate, namely the di-ester of 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane and 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoic acid, gave a level of stabilization against heat degradation which was even below that of octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate and pentraerythrityl tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoatel, used in the comparative examples of EP-A-289077.